Protective device



Ap 7, 1942. a. MAERKISCH PROTECTIVE DEVICE Filed Aug. 2, 1940 FUS/al-E Elf/VENT by Way/y 6,)44411M HIS Attorneg.

Patented Apr. 7, 1942 2.219.051 rmrscnva nnvrca Gerhard New York Maerkisoh, i General Electric Company, a

Germany, allignor corporation of Application as 2,1940, Serial N6. 349,10:

In Gernanylnly 28, 1839 4 can. (cunt-11's).

This invention relates over-voltage protective devices, and while it is not n limited thereto, it is particularly adaptable to. light- I ning arresters embodying an exponential resistance element.

' Lightning arresters made according to the principle of ionic type protectors usually include a rare gas spark gap in series with an exponential resistance element. Current flows to ground through the exponential-resistor and spark gap only when the arrester responds to an overvoltage condition, the strength of the ground current depending on the voltage of the transient wave and the resulting electrical value of the resistance. With low values of resistance the current strength may be of the order of several hundred amperes which, in general, will have no appreciable influence on the electrical properties of the arrester. As soon as the surge has passed, the power follow current is interrupted and the arrester again becomes idle.

If for any reason the exponential resistor is damaged, the usefulness of the arrester is ended the spark gap, while the lower contact I4 is electrically connected to a grounding lead ll. As indicated in the drawing, the latter connection is made through a tubular conductormember l6 which is flared out at its upper endas indicated at H to conform with the shape of the contact I. The flared end ll of the tube is connected to the contact I by a fusible element, for example, an alloy solder having a predetermined relatively low melting point while the opposite end of the tube It is suitably soldered or brazed to the end of the lead l5. Secured to the tubular member It by means of a pin it is a cylindrical member. l8, preferably of insulating material,

slidably arranged through an opening 2| in the lower part of the housing It and having a flanged head 22. A suitable spring 23 is arranged between the head 22 and the resistor disk l2.

Normally, of course, the resistance element is non-conductive and is rendered conductive only upon a predetermined abnormally high condition v of voltage, such as a lightning surge, impressed but it has not heretofore been possible to determine the exact condition of the arrester without opening it up and checking the extent of damage by actual measurement. For this reason it has been necessary periodically to inspect the various lightning arrester installations of a system to make sure they are in working order.

This is an expensive and inefficient procedure, especially in the case of pole mounted arresters.

It is an'object of the present invention to provide a new and improved lightning arrester arrangement of the general type described by which a damaged condition thereof may be readily de tected.

For a better understanding of the invention, attention is directed to the following description and the claims appended thereto taken in connection with the accompanying drawing, the sin-"e gle figure of which is a view partly in section of a lightning arrester constructed in accordance with the invention.

Referring to the drawing, a lightning arrester is shown having a housing III which may be made of glass, porcelain, or any other suitable insulating material and contains a rare gas spark gap chamber (not shown), and a series connected exponential resistance element or disk l2 having conical contacts I3 and I4 on the opposite sides thereof which element is stationarily supported upon a shoulder formed in the inner wall of the housing. The upper contact I3 connects with thereupon. Upon the discontinuance of the high voltage condition the element again becomes nonconductive. In the event that the arrester is damaged, as upon failure of the rare gas spark gap element, the arc would not be extinguished upon the passage of the surge condition and a heavy follow current would flow through the resistor excessively overloading it, The heat generated by the follow current passing through the resistor will melt the alloy solder and the end ll of the conductive tube 16 will be released from the resistor contact M. The spring 23 acting upon the head 22 of the insulator It will force it downwardly until the head rests on the bottom of the arrester housing. The lower portion of the insulator I! will protrude from the lower end of the housing through opening 2| indicating the defective condition of the arrester.

The grounding lead Ii being thereby disconnected from the resistor element i2, the arrester the remaining elements of the arrester, such as is removed from the line to safeguard it against further injury. The spring 23 is of course so designed that it will not bridge the gap between the conductive member It in its lowered posi-. tion and the resistor 12. I

The lower end of the insulator ill in the indicating position can-be readily observed at a distance, and in the case of the usual outdoor installation eliminates the necessity of climbing the transmission line pole or tower to determine the operative condition of the device.

Having described the principle of operation of my invention in what I consider to represent a preferred embodiment, I desire to have it understood that the specific arrangement described is merely illustrative and that the invention may be carried out by other means.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. A lightning arrester comprising an insulating housing having a shoulder intermediate the ends thereof, an exponential resistor element arranged in said housing and supported upon said shoulder, a current conducting member normally secured to said resistor element by fusible material, indicating means arranged within said housing. and spring means arranged between said element and said indicating means for shifting said current conducting member away from said resistor element upon the melting of said material due to an overheated condition of said element and for simultaneously moving said indicating means to an indicating position.

2. A lightning arrester comprising an insulating housing, a resistance element stationarily arranged in said housing. a current conducting member normally secured to a lower portion of said resistance element by a fusible element, indicating means operatively secured to said member and normally arranged within said housing,

and spring means operative upon the melting of said fusible element to cause said indicating means to move to an indicating position.

3. An over-voltage protective device comprising a resistance element normally non-conductive and conductive upon a predetermined abnormal high condition of voltage impressed thereupon, normally restrained spring means operative upon failure of said resistance element to reassume a non-conductive condition following discontinuance of said high voltage condition and indicat: ing means adapted to be actuated by said spring means.

4. An over-voltage protective device for a circuit comprising an element normally non-conductive and rendered conductive by an abnormal- 1y high condition of voltage impressed thereupon, said element being normally operative to reassume a non-conductive condition following discontinuance of said high voltage to preclude follow current flow therethrough, and means including a normally restrained spring responsive to the failure of said element to preclude follow current flow therethrough to disconnect said element from said circuit.

GERHARD MAERKISCH. 

